Camshaft units with camshafts that are arranged concentric to each other, also called dual camshafts, have a first camshaft that extends, as the inner camshaft, at least partially into a second camshaft as the outer camshaft. Camshaft units according to this class for actuating gas-exchange valves of an internal combustion engine are known, for example, from EP 0 582 846 B1 or U.S. Pat. No. 6,725,817. The camshaft units each have, for each camshaft, a camshaft adjuster that allows a phase shift with respect to the crankshaft. The camshaft adjuster of these camshaft units are each hydraulically actuated. Such hydraulic drives have relatively sluggish reactions in operation and temperature-dependent control values due to the oil temperature-dependent viscosity. In addition, larger adjustment angles are difficult and cannot be achieved for the previously mentioned special types of drives.
EP 1 803 904 A2 shows another camshaft unit according to the class with two camshaft adjusters. The camshaft unit has a protruding construction and requires complicated tuning of the two camshaft adjusters. The camshaft adjusters can also be arranged in the cylinder head on opposite ends of the camshafts. This increases the installation space requirements and there is no free camshaft end that could be used, for example, for attaching a fuel pump. Due to the plurality of parts to be mounted, this arrangement is also complicated in production.